China has proposed strengthening its policies on internet safety for children, which could force technology companies to make substantial operational changes to meet the new requirements.

The draft rules would require online-game operators to lock out anyone under the age of 18 between midnight and 8 a.m. They would also call for an increased number of websites to post warnings about content deemed unsuitable for minors.

Few companies will criticize Chinese policies openly. However, industry experts said that a strict implementation of the proposed rules could also force foreign companies to use Chinese censorship software that they can’t control and that could potentially serve as backdoors for Chinese surveillance.

The rules cover “smart devices,” so they would affect all makers of computing devices sold in China, including Apple Inc., Dell Inc., HPInc. and others.